Artemisinin-based combination therapies (ACTs) play an essenfial role in the current malaria control and elimination campaign. However, the circulation of counterfeit and substandard artemisinins greatly threatens the malaria control efforts. Fake artemisinins containing no or little acfive ingredients are life-threatening, while substandard drugs encourage resistance development. The scale of this 'lethal problem' is particulariy huge in some Southeast Asian countries, where as much as 64% of the artesunate sold on the market was fake. To prolong the life span of artemisinin drugs for treating malaria, strict drug quality control needs to be implemented in these nafions. For this purpose, fast and reliable methods of artemisinin detection and quanfitation are needed. Traditional methods for quantitation of artemisinins often require expensive instruments and substantial technical support, whereas the rapid qualitative method for screening of fake artemisinin derivatives is less sensifive and variable. Based on our recent success of developing a highly sensifive and reliable enzyme-linked immunosorbent assay (ELISA) using a specific monoclonal anfibody against artemisinins, we propose to 1) develop a series of monoclonal antibodies with specificities for the major artemisinin derivatives (dihydroartemisinin, artemether, arteether, and artesunate) using an innovative design of immunogens, 2) develop and optimize an ELISA for accurate quantification of artemisinins, and a lateral flow dipsfick assay for rapid, semi-quanfitafive analysis of artemisinins in anfimalarial drugs, 3) perform systematic field surveys of the drug quality of artemisinin-based anfimalarial medicines in three Southeast Asian countries using these new tools, and 4) optimize the ELISA conditions so that it can be used as an alternative tool for quantification of artemisinins and its derivatives in pharmacokinetic studies. These immunoassays will offer convenient tools for both accurate quanfificafion of artemisinins and rapid detecfion of counterfeit and substandard artemisinin derivative drugs, contribufing to anfimalarial drug quality control.